Core code has too many #define dependencies on interface-specific
defines. This means that it's currently not possible to safely
separate the core and interface code into different contexts. The
core code should be refactored to accomadate for this because we
should not have any interface-specific code in core in the first
place.

This reverts the static library SRB2Core from a7135094 and instead
adds the core sources to the SRB2SDL2 target directly.

So frustrating...

In-source builds are pain and suffering and I am going to stop people
from doing them to save them that pain.

Only when actually making the debug target though!

this is done as a POST_BUILD step

on non debug, check assets folder in src as well

silently fixing a bad malloc here too shhhhhhhhh

Generates zips only at the moment

running is another story

It is really messy at the moment. There is no support for copying the
necessary frameworks and dylibs out to the bundle for distribution, and
it is a frankenstein of manual find_library and find_package which can
sometimes pick up Homebrew dylibs.

Compiles the SDL2 target on Windows successfully